1. Field of the Invention
The present invention relates to an apparatus and a method for assembling a camera module, which adjusts a focus is performed by adjusting three axes of an image sensor module which is closely attached to a lower portion of a barrel-integrated housing disposed in a jig.
2. Description of the Related Art
With the recent development of mobile terminals such as portable phones and personal digital assistants (PDAs), the mobile terminals provide a phone call function and are used as multi-convergence devices. The most representative of the multi-convergence devices is a camera module. The resolution of the camera module changes from 300,000 pixels (VGA) to 8,000,000 pixels. Moreover, the camera module provides various additional functions, such as auto-focusing (AF) and optical zoom. Generally, camera modules are applied to various IT devices, such as camera phones, smart phones, and mobile communication terminals.
The camera modules are manufactured by using main parts of charge coupled device (CCD) or complementary metal oxide semiconductor (CMOS) image sensors. Incident light transmitted through the lens is condensed by the image sensor and is stored as data in a memory. The stored data is displayed as an image through a display medium, such as liquid crystal display (LCD) or PC monitor.
Typical camera modules are manufactured by a Chip On Film (COF) method, a Chip On Board (COB) method and the like. The COF method and the COB method will be described with reference to drawings.
FIG. 1 is an exploded perspective view of a conventional COF type camera module, and FIG. 2 is a partial sectional view of the conventional COF type camera module of FIG. 1.
Referring to FIGS. 1 and 2, the conventional camera module 1 includes an image sensor 3 for converting an image signal inputted through a lens into an electric signal, a housing 2 for supporting the image sensor 3, a lens group 4 for collecting an image signal of an object in the image sensor 3, and a barrel 5 in which the lens group 4 is stacked in multi-layers.
A flexible printed circuit board (FPCB) 6 is electrically connected to a lower portion of the housing 2. Chip components (e.g., condensers and resistors) for driving the CCD or CMOS image sensor 3 are mounted on the FPCB 6.
In the camera module 1, an anisotropic conductive film (ACF) 8 is inserted between the FPCB 6 and the image sensor 3 in such a state that a plurality of circuit components are mounted on the FPCB 6. Then, heat and pressure are applied to electrically attach the FPCB 6 to the image sensor 3, and an IR filter 7 is attached on the FPCB 6.
Furthermore, in such a state that the barrel 5 and the housing 2 are provisionally screwed to each other, the assembled FPCB 6 is fixed to the bottom surface of the housing 2 by a separate adhesive.
Meanwhile, after the housing 2 to which the FPCB 6 and the barrel 5 are coupled is fixed by an adhesive, an object (resolution chart) is set at a predetermined distance in front of the barrel 5 so as to perform focus adjustment. The focus adjustment of the camera module 1, that is, the focus adjustment between the lens group 4 and the image sensor 3 is performed as a vertical transfer amount of the barrel 5 is adjusted by rotating the barrel 5 screwed to the housing 2.
At this time, the focus adjustment is performed in a state where the distance from the object is set at 50 cm to the infinity. After the focus is finally adjusted, the housing 2 and the barrel 5 is bonded and fixed to each other by an adhesive injected therebetween.
However, when the barrel 5 screwed to the housing 2 is rotated and vertically transferred in order to adjust the focus of an image formed in the image sensor 3 after the barrel 5 having the lens group 4 mounted therein is assembled into the housing 2, foreign matters such as particles, generated by friction at the screw-connection portion between the barrel 5 and the housing 2, drop down onto the upper surface of the IR filter 7 or the image sensor 3.
Further, the assembling of the FPCB 6 and the housing 2 is determined on the basis of the IR filter 7, which means that the IR filter 7 plays an important roll of adjusting the centers of the image sensor 3 and the lens group 4. Therefore, the mounting position of the IR filter 7 has a large effect upon foreign matters.
That is, as the IR filter 7 is mounted adjacent to the image sensor 3, foreign matters dropping onto the upper surface of the IR filter 7 can be easily recognized. On the contrary, as the IR filter 7 becomes distant from the image sensor 3, an effect caused by foreign matters becomes insensible. Therefore, the camera module needs to be designed in such a manner that the IR filter 7 and the image sensor 3 are spaced at a proper distance from each other.
FIGS. 3 and 4 are diagrams showing a camera module manufactured by the COB method. FIG. 3 is a cross-sectional view of a conventional camera module manufactured by the COB method, and FIG. 4 is an exploded perspective view of the camera module.
In the conventional camera module 10, a printed board 11 having a CCD or CMOS image sensor 12 mounted thereon by wire bonding is coupled to a lower portion of a housing 13 formed of plastics, and a lens barrel 16 having a cylindrical body 15 extending downward is coupled to a barrel 14 extending from the housing 13.
In the camera module 10, the housing 13 and the lens barrel 16 are coupled to each other by coupling a female screw 14a formed on the inner circumferential surface of the barrel 14 to a male screw 15a formed on the outer circumferential surface of the cylindrical body 15.
At this time, an infrared ray (IR) filter 18 is disposed between a lens L mounted in a lower end portion of the lens barrel 16 and the image sensor 12 attached on the printed board 11, the IR filter 18 blocking long-wavelength infrared rays incident on the image sensor 12.
In the camera module assembled in such a manner, while light incident from a specific object passes through the lens L, an image is inverted so that the focus is adjusted on the surface of the image sensor 12. At this time, when a focus is optimally adjusted while the lens barrel 16 screwed to the upper end of the housing 13 is rotated, an adhesive is injected between the housing 13 and the lens barrel 16 such that the housing 13 and the lens barrel 16 are bonded to each other. Then, the camera module is finalized.
In the above-described COF and COB methods, the lens barrel 5 or 16 is inserted through the upper opening of the housing 2 or 13 and is then closely attached through the screw coupling using male and female screws formed on the inner and outer circumferences of the respective members. Further, as the height of the lens barrel 5 or 16 is adjusted at the upper end of the housing 2 or 13 by rotating the lens barrel 5 or 16, the focus adjustment between the lens L within the lens barrel 5 or 16 and the image sensor 3 or 12 mounted on the printed board 6 or 11 is performed.
Therefore, in the conventional camera modules manufactured by the above-described assembling methods, when the housing 2 or 13 and the lens barrel 5 or 16 are vertically coupled, and if the male and female screws are engaged at a distorted angle, screw threads can be broken or the coupling portion can be worn away by the friction between the male and female screws. Then, foreign matters such as minute particles can be generated, thereby degrading the assembling property.
The particles generated between the housing 2 or 13 and the lens barrel 5 or 16 inevitably drop down onto the upper surface of the IR filter 7 or 18 or onto the light reception region of the image sensor 3 or 12. Therefore, when an image is reproduced by the image sensor 12, the particles have a large effect on the image.
Further, since the housing 2 or 13 and the lens barrel 5 or 16 are coupled through screws, the lens can be tilted along the angle of the screw formed on the lens barrel 5 or 16 when the lens barrel 5 or 16 is rotated.